This invention relates to an improved temperature compensated vertical pin probing device for probing integrated circuits over a large temperature range.
Integrated circuits in their wafer state are tested using probing devices, the probes of which are traditionally of cantilevered or vertical configuration. In a known type of vertical pin probing device, the probes are held between spaced upper and lower dies and are generally curved with a straight portion that protrudes substantially perpendicular through the lower die of the housing. As the wafer under test is raised into contact with the probing device, and then overdriven a few thousandths of an inch, the probes recede into the housing, and the curved portion of the probe deflects causing spring force that provides good electrical contact with the integrated circuit pads.
Traditionally, the housing is made from a dielectric material, often a plastic sold under the trademark Delrin®, by E.I. duPont de Nemours & Co. of Wilmington, Del.
When a certain IC (integrated circuit) is tested at two or more temperatures, over a large temperature range, for example 32 degrees F., room temperature, and 275 degrees F., the typical prior art probe housing expands with a significantly higher thermal expansion rate than that of the silicon base material of the IC wafer under test. Such expansion causes a mismatch of the probe locations and the IC pad locations, a condition that not only results in failure to make satisfactory electrical contact, but may result in fatal damage to the IC due to probe penetration in the circuit region of the IC.
One solution to this problem is to dimensionally compensate the room temperature pitch dimensions of probes in the housing so that at the specified test temperature it will have expanded to provide a nearly exact match of probe and pad positions. Except for temperatures within a narrow range, this option requires separate probe devices for each specific temperature, thus greatly increasing the user's monetary investment in probe devices.
Another solution would be to find a plastic or other suitable dielectric that matches the coefficient of thermal expansion of the silicon wafer. To date, however, the most practical choices of dielectric materials have expansion rates much higher than silicon. Plastics generally have a limited high temperature capability, thereby preventing their uses for high temperature probing of IC's.
One suggestion for temperature compensation of a vertical pin probing device is disclosed in co-pending application Ser. No. 09/228,017 filed Jan. 11, 1999 in the names of W. Thiessen and A. Evans and assigned to the present assignee. That application suggested a probe comprising a pair of spacer members of a metal alloy sold under the trademark Invar® by E.I. duPont d Nemours & Co of Wilmington, Del., which has a coefficient of thermal expansion roughly equivalent to that of the silicon chip being probed. The spacer members had recesses supporting opposed channel shaped insulating inserts of a resin such as the one sold under the trademark Vespel® or a ceramic such as the one sold under the trademark Macor® by Corning Glass Works Corporation of Corning, N.Y. The ceramic sold under the trademark Macor® has a coefficient of thermal expansion significantly greater than that of the silicon chip, and required an anti-stick coating to provide the requisite lubricity to allow the probe pins to slide in the holes in the inserts. The assembly of the channel members in the recesses and subsequent drilling of the probe pin holes was a cumbersome process.
Another construction is disclosed in co pending application Ser. No. 09/228,016 filed Jan. 11, 1999 and also assigned to the present assignee. That application discloses a laminated structure of thin metal alloy foils, which may be formed a material sold under the trademark Invar®, used to support the probe pins in solid spacers, which may also be formed from the material sold under the trademark Invar® and have a coefficient of thermal expansion more closely matching that of the silicon. However, the foils are conductive and require an insulating coating to provide electrical insulation and lubricity.
It would be desirable to have a probe with all components more closely matching the coefficient of thermal expansion of the silicon chip, which is simple and easy to construct, does not require added coatings and which is suitable for high temperature probing and probing over a large temperature range.
Accordingly, one object of the present invention is to provide a temperature compensated vertical pin probing device for probing integrated circuits over a large temperature range.
Another object of the invention is to provide a vertical pin probing device which does not require application of special coatings to insulate or provide lubricity.
Another object of the invention is to provide an improved vertical pin probing device suitable for probing integrated circuits at very high temperatures, which is simple to construct.